This disclosure relates generally to an air handler for conditioning an indoor space, and more specifically to a direct evaporative air handler that can provide supply air to cool and humidify the space under different ambient operating conditions. The air handler can be used to condition data centers that require relatively consistent supply air under different ambient conditions, i.e., even during cold during winter months and hot summer months.
Data centers are used to house electronic devices, such as servers and computer storage devices, which generate a significant amount of heat during operation. Direct evaporative air handlers are used to cool data centers by providing a relatively cooler supply air stream to the enclosed space in which the electronic equipment operates. Although the operating requirements for air handlers vary depending on the data center, in general, it is preferred that the air handler deliver supply air to the data center at a temperature of about 75° F. and a humidity in the range of about 25-80%. It can be difficult to control the temperature and humidity of the supply air using direct evaporative systems in some conditions because cooling outdoor air is accomplished with discrete evaporation steps, which can render the air too cool or too humid, for example. Additionally, in very cold weather when the air is dry, it can be difficult to humidify the outdoor air without freezing the evaporative media.
One approach to improve control of temperature and humidity parameters is to control the amount of the evaporation media that is wetted, so that, depending on the outdoor conditions, only a portion of the total media surface is wetted. This method may be configured in either series or parallel split media, and provides cooling in discrete stages. Control of the supply air conditions can be difficult even under this approach. For example, if a control signal is sent to stop wetting the media, the media will remain wet for a significant period (until all of the water has been evaporated) and continue to cool and humidify the outdoor air.